Abandonware is a term for software, typically computer or video games, that are no longer for sale by conventional means, or supported by the creator. In many cases the abandoned software was distributed by websites, such as warez, for free. The use of the "abandonware" term is controversial, as distributing out of print software and games is still considered software piracy, and their copyright is not actually abandoned. Some publishers actively file Digital Millennium Copyright Act (DMCA) takedowns of abandonware and defend its copyright, while others do not. Meanwhile, some video game historians believe that this distribution is justified to preserve history given the lack of viable alternatives.

If a software product reaches end-of-life and becomes abandonware, users are confronted with several potential problems: missing purchase availability (besides used software) and missing technical support, e.g. compatibility fixes for newer hardware and operating systems. These problems are exacerbated if software is bound to physical media with a limited life-expectancy (floppy disks, optical media etc.) and backups are impossible because of copy protection or copyright law. If a software is distributed only in a digital, DRM-locked form or as SaaS, the shutdown of the servers will lead to a public loss of the software. If the software product is without alternatives, the missing replacement availability becomes a challenge for continued software usage.

Once a software product becomes abandonware, there is a high risk that the source code becomes lost or irrecoverable even for its original developers, as multiple cases have shown.

One of many examples is the closure of Atari in Sunnyvale, California in 1996, when the original source codes of several milestones of video game history (such as Asteroids and Centipede) were thrown out as trash, some of which were later recovered. After the closure of Tapulous, Tap Tap Revenge became abandonware. There is also no way to retrieve the source code due to the app being sandboxed, thus making preserving it borderline impossible.

Unavailability of software and the associated source code can also be a hindrance for software archaeology and research.

As response to the missing availability of abandonware, people have distributed old software since shortly after the beginning of personal computing, but the activity remained low-key until the advent of the Internet. While trading old games has taken many names and forms, the term "abandonware" was coined by Peter Ringering in late 1996. Ringering found classic game websites similar to his own, contacted their webmasters, and formed the original Abandonware Ring in February 1997. This original webring was little more than a collection of sites linking to adventureclassicgaming.com. Another was a site indexing them all to provide a rudimentary search facility. In October 1997, the Interactive Digital Software Association sent cease and desist letters to all sites within the Abandonware Ring, which led to most shutting down. An unintended consequence was that it spurred others to create new abandonware sites and organizations that came to outnumber the original Ring members. Sites formed after the demise of the original Abandonware Ring include Abandonia, Bunny Abandonware and Home of the Underdogs. In later years abandonware websites actively acquired and received permissions from developers and copyright holders (e.g. Jeff Minter, Magnetic Fields or Gremlin Interactive) for legal redistribution of abandoned works; an example is World of Spectrum who acquired the permission from many developers and successfully retracted a DMCA case.

Several websites archive abandonware for download, including old versions of applications that are difficult to find by any other means. Much of this software fits the definition of "software that is no longer current, but is still of interest", but the line separating the use and distribution of abandonware from copyright infringement is blurry, and the term abandonware could be used to distribute software without proper notification of the owner.

The Internet Archive has created an archive of what it describes as "vintage software", as a way to preserve them. The project advocated for an exemption from the United States Digital Millennium Copyright Act to permit them to bypass copy protection, which was approved in 2003 for a period of three years. The exemption was renewed in 2006, and as of 27 October 2009^[update], has been indefinitely extended pending further rulemakings. The Archive does not offer this software for download, as the exemption is solely "for the purpose of preservation or archival reproduction of published digital works by a library or archive." Nevertheless, in 2013 the Internet Archive began to provide antique games as browser-playable emulation via MESS, for instance the Atari 2600 game E.T. the Extra-Terrestrial. Since 23 December 2014 the Internet Archive presents via a browser based DOSBox emulation thousands of archived DOS/PC games for "scholarship and research purposes only".